U.S. Virgin Islands, 2009

Flash Flood and Heavy Rain in U.S. Virgin Islands, September 4 to 6, 2009

September 4 to 6, 2009 · NWS SJU · 3 events in 2 counties and zones

A tropical wave emerged from the coast of Africa on August 25th, which moved westward near the Cape Verde Islands on the 26th. The system organized as it crossed the Atlantic, developing a low pressure area by the 28th.

Where it happened

Every event with a place to put it. Tap one for its entry below.

  • Tornadoes
  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

Open the live radar over this ground

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
3

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS SJU wrote it up.

A tropical wave emerged from the coast of Africa on August 25th, which moved westward near the Cape Verde Islands on the 26th. The system organized as it crossed the Atlantic, developing a low pressure area by the 28th. The system became well-enough organized to be classified a tropical storm during the afternoon of September 1st. A tropical storm watch was issued for the U.S. Virgin Islands and Puerto Rico at 5 pm September 2nd, followed by a tropical storm warning at 11 am on September 3rd. The system moved generally westward, and experienced moderate vertical wind shear through most of its existence as a tropical cyclone. As the surface circulation left most of the associated thunderstorms behind, the system tracked south of due west due to the low-level flow pattern Erika was embedded within. By the 3rd of September, Erika weakened into a tropical depression at 5 pm on September 3rd, and soon devolved into a remnant low during the evening. The remnant disturbance led to heavy rains over the U.S. Virgin Islands and Puerto Rico, which caused flooding.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS San Juan, PR wrote its last area forecast discussion before the first event at Sep 3, 8:39 PM AST, 3 hours 21 minutes earlier.

Area forecast discussion, Sep 3, 8:39 PM AST, 3 hours 21 minutes before
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The radar

The San Juan radar (TJUA), 142 km away, was scanning. The volume nearest the first event began at 03:56 UTC.

Open the radar archive at this moment

Event by event

2 heavy rain, 1 flash flood. Local standard time, as filed.

Heavy Rain, St. Croix

When
September 4, 12:00 AM AST to September 5, 12:00 AM AST
Where
St. Croix County, 3 mi SW of St Croix
Reported by
ASOS
Coordinates
17.700, -64.813

Saint Croix airport ASOS sensor reported 1.41 inches for the 24 hour period.

Heavy Rain, St. Croix

When
September 5, 12:00 AM AST to September 6, 12:00 AM AST
Where
St. Croix County, 6.66 mi W of St Croix
Reported by
COOP Observer
Coordinates
17.713, -64.880

Spotter reported 1.61 inches for the 24 hour period.

Flash Flood, St. Thomas

When
September 5, 11:19 AM AST to 12:15 PM AST
Where
St. Thomas County, 1.41 mi SW of St Thomas to 1.31 mi SW of St Thomas
Cause
Heavy Rain
Reported by
Emergency Manager
Coordinates
18.338, -64.947

Flash flooding was reported along Veterans Highway close to Banco Popular building.

What these are

Heavy Rain
Rainfall totals unusual for the place and season that did not produce a flood.
Flash Flood
Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in U.S. Virgin Islands in 2009Every state in 2009This day in weather historyWarnings in U.S. Virgin Islands, September 2009

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 187302, 187246, 196891.